High frequency gaseous conduction lamp



June 4, 1935. s. c. WHITMAN HIGH FREQUENCY GASEOUS CONDUCTION LAMP Filed April 18, 1952 2 Sheets-Sheet l IN V EN TOR. y

I June 4, 1935.

S. C. WHITMAN HIGH FREQUENCY GAsEoUs CoNDUcTloN LAMP Filed April '18, 1932 2 Sheets-Sheet 2 INVENTOR.

Z www M' fameux G, Qf/Y X gym Patented June 4, 1935 Y uNlTEos'rATEs v 2,003,410 a mon FREQUENCY GAsEoUs coNnUotl'roNA stewart c; Wham, .mma Heights, N. Y. Application April 1a, 1932, serial No. 605,990 25 claims. (ci. 176-122) This invention relates to new and useful lmfprovements in the art of recording sound on film and more particularly to a gaseous conduction lamp operated by radio frequency energy to ac- 5 complish the desired result, this application being a continuation in part of my copending application, Serial Number 507,220, flied January 27, 1931. An object of the invention resides in the production of a lamp wherein the respective glows fromf a pair of electrodes occupy the same space. A further object of the invention is to produce a lamp of high actinic value. l A still further object is to provide a lamp whose light source is of optimum size, shape, and brilliancy for the necessary optical reduction.

Still another object of the invention is to provide a lamp of rugged construction and one capable of long life.

With these and numerous other objects in view, my invention'consists in the novel features of construction, combination and arrangement of parts as will be hereinafter referred to and more particularly pointed out in the specication and claims. y

In the accompanying drawings forming a part of this application:

Figure 1 is a side elevation, with partsbroken away and parts in section, showing a lamp constructed in accordance with my invention;

Figure 2 is a horizontal section as seen on the line 2-2 of Figure 3;

Figure 3 is a vertical section as seen on the line 3-3 of Figure 2;

Figure 4 is an elevation with parts broken away and parts in section illustrating "a modification of my invention;

Figure 5 is a similar view thereof taken on a K plane at right angles to the plane of Figure 4;

40 Figure 6 is an enlarged fragmentary vertical section as seen on the line 6 6 of Figure 5;

Figure 7 is a similar view as taken on the line 1-1 of Figure 6; and A Figure 8 is a horizontal 45 line 8 8 of Figure 6.

s In the recording of sound on illm, the photographic record is usually in the form of narrow discrete parallel lines on the edge of the illm.

The width and the density of these lines are responsible for the frequencies and'volumes oi the recorded sounds. For this reason,` it is desirable that the modulated light source producing this photographic record be rectangular in shape.

Itisalsodesirablethatthevariatlonlnsound section as seen on the intensity to be photographed be faithfully-'fol'- lowed by the intensity. .of lightemitted from the lamp. It is my purpose to' describe here a lamp which best fullls these requirements.

Figure 1 shows a side elevation of a preferred .,g form. Figure 2 shows a horizontal cross section and Figure 3 a vertical cross section. Inasmuch as alternating current is to be used in con-r nection with this lamp, the two electrodes must be of equal area since they act alternately asilo cathodes. 'Ihe area of these electrodes must be carefully determined so that the required light intensity may be obtained without prohibitive disintegration. It is desirable to conne the glow discharge between the two inner. surfaces of these electrodes in order to obtain a clearly defined rectangular source of light. For this reason, the outer surfaces of the electrodes are shielded with an insulating material. The lead wires and support wires electrodes are also shielded in order to conne the glow between the rectangular electrodes, 'Ihe distance at which the electrodes are spaced from each other is a function of current density, 886 pressure and electrodematerial. Taking these' factors into consideration, the spacing is adjusted i so that the cathode glows surrounding each electrode apparently overlap and the apparent widthof the arc between the electrodes is. constant. Thus, during operation the light source appears J as a brilliant thread of light between the electrodes with a narrow dark space adjacent to the surface of each. As the impressed voltage 'increases, the dark space surrounding each electrode shrinks slightly and the width of the luminous portion of the arc increases. 'I'his is undesirable since the linearity of intensity is inipaired. Therefore, the electrodes are mounted' to converge slightly toward the top, that is, nearest the nlm. Thus, when the luminous discharge becomes wider or occupies a greater part of the area between the electrodes, the mean center of' light is brought closer to the ilm. In this man-` ner, the 'variation in the width of the arc iscompensated for. Under proper conditions, the lu- 4,5, minous portion of the arc and the dark spaces can be made toV appear stationary, unchanging in dimensions, and varying only in-intensity under the inuence of a modulated signal voltage.

The components are assembled sothat'the area of the glow does notchange with the-change in signal intensity. This results in a change in light intensity only. The 'electrode material must be chosen so that the glow does not become` spot since this would cause a change'ln the runningtothese'gA mean intensity distance with respect to the film. The electrodes must be small enough to result in recording light intensities on available power and the proper material selected to prevent undue sputtering. Since mercury constitutes part of the gas filling contained in the lamp, the Vapor pressure of the mercury at the operating temperature must be considered in reference to the darkspaces and arc widths discussed above. This is .accomplished by choosing the proper length of glass envelope for the proper heat radiation. As is well known, the mercury vapor pressure in a lamp of this type is determinedby the coolest part of the envelope.

Using a lamp constructed according to the present invention, a very simple optical system may be constructed to be used therewith. Since this is the case, the optical system may be constructed economically of quartz. Hence, the lamp envelope may be Aeconomically constructed of Uviol, Ultrasol, or Corex glass, and advantage taken of the actinic ultra-violet radiation. Inasmuch as a large percentage of the light radiated is a result of the mercury discharge and inasmuch as the mercury vapor pressure is very low, ultra-violet radiation of short wave length is emitted. In fact, the most prominent radiation is of wave length 2537 A. U. as a result of the Pz-Da energy level transition. This light is extremelyy active actinicly and constitutes one reason why the mercury vapor pressure is kept Having explained these interdependent relations, I will now describe a commercial adaptation which has been found to work very satisfactorily.

In describing the invention, I shall refer to the drawings in which similar reference characters designate corresponding parts throughout the several views. Referring to Figure l, the tubular glass envelope 6 of Corex glass of approximately eight inches by one inch is utilized. This envelope is substantially flat on the top. The two rectangular electrodes of dimensions one centimeter by two centimeters, are mounted on the glass stem 1. The electrodes are mounted on the shielded support wires I2 and the lead wires 8 and 9 sealed thereto. I have discovered that electrodesv made of a chromium iron alloy or preferably of beryllium are most advantageous for my purpose to reduce electrode disintegration to a minimum. The spacing between the electrodes is 1.2 millimeters at the bottom and 1 millimeter at the top. The electrodes are shielded with mica sheets I3 on the outer surface secured thereto by clips I4 and the glow thereby insulated from these portions. The electrodes may be mounted very close to the flattened top portion of the envelope, in order to bring the light source as close as possible to the lm. By this construction, a rugged mount results which is free from vibration effects. I have found that any such vibration results in small changes in arc width which further results in a superimposed frequency modulation in the recorded sound. The lamp thus constructed-is exhausted in the usual manner, care being taken to degasify the metal parts.

In this particular adaptation of the invention, I have found a mixture of mercury vapor and argon as most satisfactory. A small drop of pure mercury is distilled into the lamp and spectroscopically pure argon admitted to a pressure of 12 millimeters of mercury.

I have found in experimenting with my invention as hereinabove described that certain genof the insulator is open eral relations exist among the various factors entering into the construction of the lamp. The most desirable gas filling consists in a mixture of an inert gas such as argon, neon or helium at pressure of from ve to 20 millimeters, and mercury vapor at a pressure corresponding to temperatures of from 30 to 50 C. Using this gas filling, best results are obtained by operating the lamp at current densities of .030-.040 4ampere per square centimeter of electrode area. The ratio of electrode spacing in millimeters to gas pressure measured in millimeters of mercury may cover a range of 1-8 to 1-12.

I have further found that a ratio of approximately 10 to 1 between electrode height and spacing dimension thereof is productive of maximum brilliancy for given input power.

In Figures 4 to 8, inclusive, I have shown a slight modiiication of my invention, wherein the Velectrodes are provided with a more effective shielding means than that illustrated in the previously described adaptation of my invention. In this form of the invention so illustrated the lamp includes an envelope I5 of the same character and shape as that previously described. The stem I6 therein includes the three glass tubular upstanding projections I1, I8, and I9, respectively. The projections I1 and I9 are provided with bores'through which extend lead-wires 20 which connect respectively with electrodes 2|. These particular electrodes 2| are similar to the electrodes of the previously described form. In extending the lead wires 20 through the projections |`I and I9, protection against electric discharge is afforded at these points. Enclosing the electrodes 2| is an insulating member 22 composed of a refractory insulating material. This insulator is rectangular in cross section and the inner faces of its end walls are slotted as shown at 23 to receive the electrodes 2| as clearly shown in Figure 8. A bottom wall 24 is formed on this insulator which restsvupon the upper peripheral edges of the upstanding projections I1, I8, and I9. Formed on said bottom wall is a depending tubular neck portion 25 which receives therein the projection I8 forming a rigid support for the insulator. This construction is clearly shown in Figure 6 of the drawings, wherein is also disclosed openings 26 in the bottom wall 24 through which extend the lead-wires 20. The upper end portion to provide a restricted aperture through which the light is emitted.

With the use of such an insulator as I have herein described and shown, it will be seen that no undesirable discharges can take place except between the inner faces of the electrodes.

While I have particularly described the elements best adapted to perform the functions set forth, it is obvious that proportion and in the minor details of construction may be resorted to, without departing from the spirit or sacrificing any of the principles of the invention.

Having thus described the invention, claimed is:

1. In a gaseous conduction lamp, a pair of rectangular electrodes of equal areas formed of a metal surfaced with beryllium, the ratio of whose length to height is approximately two to one.

2. In a gaseous conduction lamp, a pair of substantially parallel spaced electrodes of equal size what is and shape having a ratio of approximately ten to various changes in form,

3. In a gaseous conduction'lamp, a partially evacuated envelope, a pair of substantially parallel spaced electrodes therein of equal areas and a mixture of argon and mercury vapor contained in said envelope, the pressure of said mixture measured in millimeters being in the proportion of approximately ten to one with respect to the spacing in millimeters between the electrodes.

4. In a gaseous conduction lamp, a partially evacuated envelope, a pair of substantially parallel spaced electrodes therein of equal areas formed of a metal surfaced with beryllium, and a mixture of argon and mercuryvapor contained in said envelope, the pressure of said mixture measured in millimeters being in the proportion of approximately ten to one with respect to the spacing in millimeters between the electrodes.

5. In a gaseous conduction lamp, a partially evacuated envelope, a pair of substantially parallel spaced electrodes therein of equal areas, and

a mixture 'of argon and mercury vapor contained in said envelope, the pressure of said mixture measured in millimeters being in the proportion of approximately ten to one with respect to the spacing in millimeters between the electrodes.

6. In a gaseous conduction lamp, a partially evacuated envelope containing a mixture of argon and mercury vapor, and a pair of spaced electrodes of equal areas tending to converge upwardly, the pressure of said gaseous mixture measured in millimetersv being in the proportion of approximately ten to one with respect to the spacing in millimeters between the electrodes.

'7. In a gaseous conduction lamp, a partially evacuated envelope containing a mixture oi.' argon and mercury vapor, and a pair of spaced electrodes oi' equal areas formed of a metal surfaced with beryllium, tendingto converge upwardly, the pressure of said gaseous mixture measured in millimeters being in the proportion of approximately ten to one with respect to the spacing in millimeters between the electrodes.

8. In a gaseous conduction lamp, a partially evacuated envelope containing a mixture of argon vand mercury vapor, and a pair of spaced electrodes of equal areas formed of a metal surfaced with beryllium, said electrodes being mounted to converge together toward one end of said envelope.

9. In a gaseous conduction lamp unit, a partially evacuated envelope containing a mixture of inert gas with mercury vapor, and a pairof spaced electrodes mounted therein, said electrodes being of such areas andl in such relative positions that their respective cathode glow discharges can be made to occupy thesame positions in the space between said electrodes by regulating the current value, and means for limiting the current value to cause said glow discharges to be spacially coincident.

10. Infa gaseous conduction lamp, a partially evacuated envelope, a pair of substantially parallel spaced electrodes therein of equal areas and. a mixture of argon and mercury vapor contained 'in said envelope, the pressure oi' said mixture measured in millimeters being in the proportion of approximately ten to one with respect to the spacing in millimeters between the electrodes, and an insulating member housing said electrodes and provided with a restricted light passage at one end thereof. Y

11. In a glow lamp unit for sound on illm recordlng purDOses, a glass envelope, agas lling, two glow discharge electrodes of equal areas, said electrodes being of such areas and in such relative positions that their respective cathode glow discharges can be made to occupy the same positions in the space between said electrodes by regulating the current value, and means for limiting the current value to cause said glow discharges to be spacially coincident.

12. In a gaseous conduction lamp, a partially evacuated envelope, a pair of substantially parallel spaced electrodes therein of equal areas, and

a noble gas contained in said envelope having a pressure measured in millimeters being in the proportion of approximately ten to one with respect to the spacing in millimeters between the electrodes.

13. In a gaseous conduction lamp, a partially evacuated envelope, a pair of substantially par-1 allel spaced electrodes therein of equal areas, and a mixture of a noble gas and mercury vapor contained in said envelope, the pressureof said mixture measured in millimeters being in the proportion of approximately ten to one with respect to the spacing in millimeters between the electrodes. I

14. In an electrical optical -reproducing system, a gaseous conduction lamp comprising an envelope and a pair of electrodes oi substantially equal areas positioned adjacent each other but in spaced relation, and mounted in said envelope, said envelope being lled with a lnoble gas of determined pressure, and a source for applying to said electrodes an alternating potential of such value that the discharge between said electrodes corresponds to a current density vof substantially 0.03 to 0.04 ampere per square centimeter of electrode area.

15. In a gaseous conduction lamp unit, a gaseous conduction lamp comprising an envelope and a pair of electrodes of substantially equal areas positioned adjacent eachother but in spaced relation and mounted in said envelope, said electrodes being mounted to mutually diverge toward the end from which they are mounted, said envelope being lled with an inert gas of determined pressure, and a source for applying to said electrodes an alternating potential of such value that the discharge between said electrodes corresponds to a current density of substantially 0.03 to 0.04 ampere per square centimeter of electrode area.

16. In a gaseous conduction lamp unit, a gaseous conduction lamp comprising an envelope and a pair of electrodes of substantially equal areas positioned adjacent each other but in fixed spaced relation and mounted in said envelope, said envelope being filled with'an inert gas of determinedpressure, `and a source for applying to said electrodes an alternating potential of such value that the luminous discharges between said electrodes corresponding to successive opposite halves of a cycle overlap over substantial-- ly their entire areas, whereby a line source of light of substantially unchanging area is produced without apparent ilicker.

17. In a gaseousv conduction lamp unit, a gas- .eous conduction lamp comprising an envelope and a pair of electrodes of substantially equal areas positioned adjacent each other but in xed spaced relation and mounted in said envelope.

said electrodes being mounted to' diverge 'toward electrodes corresponding to successive opposite halves of a cycle overlap over substantially their entire areas, whereby a line source of light of substantially unchanging area is produced without apparent flicker. l

18. In the operation of a gaseous conduction lamp having a pairl of fixed electrodes of equal area and a filling of inert gas, the method of obtaining -a line source of light which consists in applying to said electrodes an alternatingpotential of such value that the luminous glows between said electrodes corresponding to successive opposite halves of a cycle overlap over substantially their entire area.

19. In a gaseous conduction lamp to operate at a determined alternating potential, an envelope, a pair of electrodes of substantially equal areas positioned adjacent each other but in fixed spaced relation and mounted in said envelope, said envelope being filled with a noble gas at a pressure such that the ratio of gas pressure measured in millimeters of mercury to electrode spacing in millimeters is approximately ten to one, lsaid electrodes having such area that at said pressure and said determined alternating potential the discharge current density is approximately 0.03 ampere per square centimeter of electrode area.

20. In a gaseous conduction lamp to operate at a determined alternating potential, an envelope, a pair of electrodes of substantially equal areas positioned adjacent each other but in fixed spaced relation and mounted' in said envelope, said electrodes being mounted to mutually diverge toward the end from which they are mounted, said envelope being filled with a noble gas at a pressure such that the ratio of gas pressure measured in millimeters of mercury to electrode spacing in millimeters is approximately ten to one, said electrodes having such area that at said pressure and said determined alternating potential the discharge current density is approximately 0.03 ampere per square centimeter of electrode area.

21. In'a recording lamp, an envelope having one flattened end adapted to be positioned adjacent a record lm, a pair of adjacent but spaced electrodes of equal areas mounted adjacent the flattened end of said envelope to mutu` ally converge together toward said flattened end, and a noble gas in said envelope, the pressure proportion of'approximately ten to one with respeci; to the mean spacing in millimeters between said electrodes.

22. In a gaseous conduction lamp, an envelope having a flattened end, a pair of spaced electrodes of substantially equal areas mounted in said envelope adjacent said flattened end to mutually converge toward said iiattened end with such slope that their spacing apart is about 0.2

millimeter less at the ends of said electrodes near said flattened end of said envelope than at the other ends of` said electrodes, and a noble gas in said envelope, the pressure of said gas measured in millimeters being in the proportion ot approximately ten to one with respect to the mean spacing in millimeters between said electrodes.

23. In a gaseous conduction lamp. an envelope, an insulating member provided with a central rectangular aperture open at one face of said insulating member but closed at the opposite face, a pair of electrodes insulated from each other, means for maintaining said electrodes respectively in position against the long sides of said rectangular aperture in spaced relation to each other, and means for mounting said insulating member in said envelope.

24. In a gaseous conduction lamp, an envelope, an insulating member provided witha central rectangular aperture open at one face of said insulating member but closed at the opposite face, a pair of electrodes insulated from each other, said insulating member being provided with terminal slots at each end of the long faces of said rectangular recess, said slots being adapted to respectively receive said electrodes and hold them tightly against the long faces of said aperture, and means for mounting said insulating member in said envelope.

25. In a gaseous conduction lamp, an 'envelop an insulating member provided with a central rectangular aperture open at one face of said insulating member but closed at the opposite face, a pair of electrodes insulated from each other, means for maintaining said electrodes respectively in position against the long sides of said rectangular aperture in spaced relation to each other, and means for mounting saidinsulating member in said envelope, said electrodes being so mounted that they converge toward the open end of said aperture.

STEWART c. Wrirrmuln.

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